Underlayment Replacement

The shingles are 8-15 years old and pass a physical inspection — no curling at edges, no clawing, no granule loss patterns indicating mat fracture, no missing tabs, full adhesive seal on every course. Shingles past 15-18 years generally don't justify the strip-and-relay labor because their remaining life doesn't pay back the investment.

Manufacturer rep agreement. On warranty disputes — where the homeowner is making a claim against a GAF, CertainTeed, or Owens Corning warranty and the manufacturer's inspector confirms underlayment was the failure point — the manufacturer may cover the underlayment replacement under the labor warranty. We coordinate with the manufacturer rep on these claims.

Ice dam recurrence at the eaves. NJ Uniform Construction Code R905.1.2 requires ice & water shield 24" past the inside wall plane. Many pre-2000 NJ installs predate this requirement. When ice dams are causing recurring eave leaks on a sound shingle field, retrofitting ice & water shield at the eaves (which requires a strip of the lower 3-4 courses) is a targeted fix.

Valley underlayment failure on closed-cut valleys. When a closed-cut valley is leaking because the original installer used felt under the valley instead of ice & water shield, strip-and-relay of the valley shingles plus ice & water shield install is the proper repair.

Re-roof preparation for a future PV solar install. Some installers strip shingles, upgrade underlayment to synthetic + ice & water shield, and relay shingles as part of a solar-PV prep project — extending the roof life to match the 25-year solar warranty.

15-lb roofing felt is the legacy underlayment — asphalt-saturated paper, used for 100+ years. It wrinkles in summer heat, tears at fasteners, doesn't lay flat, and only provides about 8-12 weeks of weather protection if the roof is opened up. Cheap but not durable.

Synthetic underlayment (GAF Tiger Paw, CertainTeed RoofRunner, Owens Corning ProArmor) is woven polypropylene or polyethylene. It's walkable (won't tear under foot traffic), doesn't wrinkle, lays flat, provides 6+ months of weather exposure resistance, and lasts the life of the shingle install. Standard on every new install we do.

Synthetic adds about 15-20% to the underlayment line item over felt but eliminates a future failure mode. The cost difference is trivial in the context of a full replacement; on a standalone underlayment-replacement project, the upgrade is mandatory — we don't put felt back on an existing project we just stripped.

GAF Tiger Paw and similar high-temp synthetics also meet the requirement for high-temp underlayment under metal roofing — important if there's any future plan to convert from shingle to standing-seam.

Strip the existing shingles carefully, working in sections to maintain weather protection. Salvageable shingles (clean, full adhesion seal intact) get stacked for relay; damaged shingles get tossed and replaced with color-matched new from our in-stock supply.

Strip the existing underlayment completely. Felt typically comes off in strips; older synthetic comes off more cleanly. The deck is exposed and inspected as part of this step.

Decking inspection. We probe every sheet for soft spots while the deck is exposed — replace rotted sections per the decking-repair scope, document with photos. This is the moment when hidden decking issues get caught.

Install new underlayment system: ice & water shield at eaves (24" past inside wall plane minimum), valleys, and around penetrations; synthetic underlayment over the rest of the deck.

Relay the shingles in the original pattern using new fasteners. Damaged shingles replaced with color-matched stock. New flashing details where original flashing was failed or improperly installed.

Even on a relay project, we recommend new pipe boots, new step flashing at sidewalls, and a new ridge vent if the original ventilation was inadequate. Don't put failed accessories back on a freshly underlayment'd roof.